On Thu, Oct 24, 2013 at 04:49:56PM +0100, Russell King - ARM Linux wrote: > On Thu, Oct 24, 2013 at 01:55:31PM +0100, Steve Capper wrote: > > On Thu, Oct 24, 2013 at 01:23:06PM +0100, Russell King - ARM Linux wrote: > > > On Thu, Oct 24, 2013 at 11:51:44AM +0100, Steve Capper wrote: > > > > Hi Russell, > > > > I've given this a quick go on an Arndale with LPAE, and have a few > > > > suggestions below. > > > > > > Thanks. > > > > > > > > diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h > > > > > index 5689c18..d7682cd 100644 > > > > > --- a/arch/arm/include/asm/pgtable-3level.h > > > > > +++ b/arch/arm/include/asm/pgtable-3level.h > > > > > @@ -140,6 +140,7 @@ > > > > > PMD_TYPE_TABLE) > > > > > #define pmd_sect(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == \ > > > > > PMD_TYPE_SECT) > > > > > +#define pmd_large(pmd) pmd_sect(pmd) > > > > > > > > Could we please instead do something like: > > > > #define pmd_large(pmd) (pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT)) > > > > > > > > This matches the logic used in the huge pages patches (it picks up the > > > > PROT_NONE case) that would be missed above. > > > > > > Is this used in the generic parts of the kernel? Can you please point > > > out where? > > > > > > > Apologies I was a little vague. I don't think there are any PROT_NONE > > protected kernel huge pages, I am worried that pmd_huge may be used by > > other code (and then run into problems with PROT_NONE). > [I erroneously referred to pmd_huge here, I meant pmd_large sorry]. > Well, the obvious question is: why would you want pmd_large() to return > false if there is a section entry in place? Hi, for LPAE: I want pmd_large to return true for all non-zero pmds that have bit #1 clear. Clearing bit #0 of a pmd produces a faulting entry, and this is how PROT_NONE protection is enforced by huge pages. pmd_sect will return false for non-zero pmds that have both bit #0 and bit #1 clear, thus will return false for some huge pages. Cheers, -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
